Serious Trouble w/ Dellorto's -Any Pros?

914Ghost · 11-28-2003, 08:02 PM

Okay- Anyone know dellorto's really well?
Its a couple weeks later and I recieved the 40mm DRLA's I bought from ALFA whatever via e*&y...
I'm guessing these are Fairly old carbs in pretty good shape.
I gave them a quick once over and bolted them on.
Started easily, lots of smoke, and backfiring.
I warm it up, and start adjusting.
It revs smooth, idles...so/so. All injector nozzles work great.
But it sounds like a 917 K30 when you 1/4-full throttle it.
Like raw gas out the exhaust and backfires rapidly, loudly, and continuously. Car jerks and power is on/off.
No amount of adjusting in several hours yielded much better results.
**?Carbs came with block off plates for the little lever on the side of each carb. One was installed. I havent ever seen this lever before, it actuates a small piston inside the carb, and is spring loaded. Piston moves up/down and sort of "chokes" the carb.
Any advice on these things...block off or no?
On my 36's the piston bore has a brass plug in it and the carb casting is blocked to delete the piston/lever assembly.
I guess I need the Dellorto tech book..?
Any help with these things appreciated.
Regards,
Robert O

skline · skline's Garage

Sounds like the accelerator pumps. I also think I mentioned that the carbs from over in Europe are different from the ones here. I have the Dellorto book. It really doesnt give much on troubleshooting. Did you have carbs before? What cam are you running? What distributor are you running? All of these are factors.

914Ghost · 11-28-2003, 08:51 PM

Scott-
I have a set of 36 DRLA's also, I believe the cam is 'probably' the stock FI cam, and I'm running a 009 distributor. 8 deg b-tdc.
The 40's have 30mm vents, and close to the same jetting.
The injector nozzles work great, nice straight stream.
It runs okay with the 36's, but for some reason those particular carbs are having chronic problems...runs awesome one day, crappy the next...for no reason I can find.
I figured the euro carbs could be alittle different....but it cant mean they're useless or un-usable.
I'm fairly sure the arm/linkage/piston deal has something to do with it. Maybe its supposed to operate WITH the thottle, it looks like it has about the same throw..but then why the blockoff?
I'm sure I'll spend the WHOLE day tomorrow on it too.
Thanks for the thoughts though, if the book says anything about the piston I'd be interested.
Regards,
Robert O
p.s. the good news is the 40's dont whistle!

synthesis · 11-29-2003, 05:40 AM

I just saw another set of the del's from that alfa guy, is he in the states or in europe? Says both in his profile.

How do the del's compare to 40 idf webbers?

thanks,
dr

Jake Raby · 11-29-2003, 07:52 AM

The Alfa Carbs are TOTALLY mistuned for a VW engine. They have the wrong Venturis, and every het is goofed. Do this:

Call CB Performance 800 274 8337, tell them you need the following.

34mm Venturis (yours are probably 30mm now)

180 air correction

.2 Emulsion tubes (there is a number before the .2, but thats the suffix that matters)

60 idle jets

45 pump jets

one set each of 135 and 140main jets

This should set you up well. The Alfa carbs are a complete different creature from the factory than other dells.

I use these carbs alot and can tune them blindfolded (Have done it) Other than that ensure that the float heights are set correctly and evenly on both carbs..... Have fun, let me know if my recipe works for you!

914Ghost · 09:11 AM

Well, its close to what you're prescribing:
30 mm Vents
180 Air Correction
.2 Emulsion
I have 50 Accel Pumps in now, they came with 33.
Main jets are 122..
and they have 60 Idle Jets.
IS it all about Venturi size?
And what about the piston? I forgot to mention the linkage for it has a barrel/pinch nut where a cable should hook to it.
I can delete the linkage with the block offs and leave the piston in with the spring above is pushing 'down'. Then it doesnt move.
Or remove the piston all together...I may have to try both.
back to the garage..
Regards,
Robert O

thesey914 · 09:36 AM

So are you saying that one carb has the accelerator pump blocked off? It gives a squirt of fuel straight down the choke to smooth out flat spots when the throttle is opened.
I rebuilt my carbs and got the diaphragm round the wrong way on one carb, so the accelerator pump wasn't functioning. The car ran horribly as you described. when I figured out that it was the diaphragm and rectified it -problem solved.

Is this what you're talking about?
My Delll 45's

Quote:

Originally posted by synthesis
How do the del's compare to 40 idf webbers?

Its my understanding that the Dells are superior to the Webers

914Ghost · 10:42 AM

No NO NO....pssh..
Not the accelerator pump. Both accelerator pumps are great, injector nozzles clear, good stream.
On the other side of the carb (both carbs) theres an arm that a cable can hook to, the arm 'rotates' and actuates a piston that moves up under tension...at rest it is in the down position.
When the car is runing, and the piston is moved 'up', it sounds like it opens a duct or vent...VERY loud suction noise, and RPM increases.

How do you post a picture..? I could show you the arm/linkage.
And even inside the carb where the piston is.

Another hint maybe?- Idle is smoothest, with all mixture screws turned all the way in.

I'll work on it some more...But I think it has something to do with that piston. It should probably be blocked off/removed all together and the bore plugged...I dunno.
Thanks for you help though, we'll figger it out.
Robert O

Hows this:

914Ghost · 11-29-2003, 10:45 AM

Thats basically the thing on both carbs.
A cable would go through the end and hook to the brass fitting in the center- pulling (on this side, pushing on the driver side)
actuates the piston.

??? Eh?
Regards,
Robert O

Jake Raby · 11-29-2003, 12:00 PM

If the mixture controls idle best all the way in. The idles are rich. Go down a size or trim it till it ppurrs at one turn out the best.

The vents will cause some major isues with the set up you have. the 34mm vent changes alll the jetting, so do that first, and the jets may be okay in the idles..

can you take a pic of your emulsions? No Fiat carb I have ever seen has had the correct emulsions, before being converted. I can tell by looking at them.

I used to buy these carbs from wrecking yards in the UK, rebuild them, convert them, and sell them. I have rebuilt 65 in one week before!

The port omn the side is for an enrichment system. Retain it and hook them to a cableor electronic solenioid for a choke on cold mornings. Or remove it and block it off with a piece of aluminum. They can also be left in place and not harm anything. if these are sticking they can cause rich running in the midrange, or basically all the time.. Check them.

These are good carbs, but the Fiat models are different, and always need converting for our engines.

914Ghost · 11-29-2003, 04:00 PM

Jake-
you kick ass, thanks.
When you say block it off (makes the most sense) do I leave the piston in there? Or remove it all together?
My emulsion tubes are teh same on my 36 DRLA's, identical- so I think theyre probably okay.

And:
" Go down a size or trim it till it ppurrs at one turn out the best. "
Trim the mixture screws..so they seat further in? hmm...I dunno
Never done it but, its just crazy enough to work!!

We'll see. I'm buying the tech book.
Regards,
Robert O

Jake Raby · 11-29-2003, 04:43 PM

NO DO NOT CUT THEM!

What I meant was "Trim" the jetting to the point that you idle the best at one full turn from bottom at 1,000 RPM. Anything less than 3/4 turn means that you are rich... anything that needs more than 2 turns out from bottom is lean. Go up asize and try readjusting.......

You can use a can of starting fluid to apply a "Sniff"over the carb tops. If the engine falls off with the "Sniff" you can safely say that you are a tad rich, or just right. If it falls off alot, then you are really rich....

Same goes for being lean... apply the "Sniff" over the carb tops and if tghe engine speeds up or smoothes out the idles are lean- go up a size.

Just be careful, Ether is dangerous. I'm not responsible for 3rd degree burns, or your hospitalbills should you go out in a ball of fury..

914Ghost · 11-29-2003, 06:11 PM

Sorry,...yeah, the grinding the mixture screws was supposed to come across as sarcasm. Its so hard to type sarcasm....

Anyhow, I'm gonna try to get 34mm vents and see what that does.
Thanks for your help though, I've had the carbs off again, and thoroughly checked them, and have disabled the 'enrichment' piston doodad in a big way. It sacts like it dumping fuel yet the plugs read a little lean. Mixture adjustment does almost nothing.
The way it is the car is undrivable, it's that bad- it doesnt just miss, or backfire...it really cant be driven- ANY throttle causes repeated backfiring both through exhaust and carbs. Sound like mismatched mains/veturis?
Regards,
Robert O

Jake Raby · 11-29-2003, 06:50 PM

Sounds like you possibly have 'Dellorto Drip" with the engine off turn on the fuel pump and see if small droplest of fuel leak into the bores....... This is common with Dells. It can be repaired and will give symptoms of non tunability- Just like you describe